Several synthetic polymers containing vinyl lactams are presently used in cosmetic and textile formulations to provide high penetration of other active components, to contribute body and holding power to hair sprays, setting lotions, etc. and to promote softening and moistening in skin and body conditioners. Most of these synthetic polymers are comprised of vinyl lactam and acrylate or methacrylate monomers as in U.S. Pat. Nos. 3,954,960 and 3,914,403. While these copolymers provide excellent hair adhesion and set hold under conditions of high humidity, they are subject to excessive hydrolysis when formulated into cosmetic formulations at a pH greater than 7 and/or maintained at a elevated temperature, for example temperatures in excess of 40.degree. C., for considerable time. Hydrolysis causes the polymer to decompose forming an alcohol amine which can result in significant lowering of viscosity and concomitant reduction in beneficial properties.
While the polymer of U.S. Pat. No. 4,057,533 overcomes some of the above disadvantages, such polymers containing the aminomethyl acrylamide moiety of this patent are known to be unstable and to decompose to methylol amide and an ammonium salt upon heating (see U.S. Pat. No. 2,344,934) or in the presence water (Journal of the Society of Dyers and Colourists, Volume 63, page 260, 1947 by F.V. Davis and SURFACE ACTIVITY, Van Nostrand Press, 2nd Edition, 1961, page 241 by J.L. Moilliet, B. Collie and W. Black). Other processes for producing amino acrylamide lactam copolymers result in prohibitative amounts of toxic unreacted quaternized monomer which render the polymeric product unsuitable for cosmetic formulations and personal care treating applications.
Accordingly, it is an object of this invention to minimize or eliminate the process disadvantages discussed above and to provide a less contaminated product which can be employed directly in sensitive areas of application such as in cosmetic or medicinal formulations.
Another object of the invention is to provide a commercially feasible and economical method for the manufacture of high molecular weight vinyl lactam-quaternized acrylamide copolymers.
Still another object is to provide an improved copolymerization process which is carried to completion within a shortened period of time.
Still another object is to maximize the efficiency of polymerization initiators in the copolymerization of a vinyl lactam and a quaternized acrylamide.
Yet another object is to provide a high molecular weight vinyl lactam/quaternized amino acrylamide copolymer having less than 0.1 wt. % residual monomer.
These and other objects will become apparent from the following description and disclosure.